This relates generally to integrated circuits, and more particularly, to integrated circuits with wireless communications circuitry.
Wireless integrated circuits such as transceiver circuits and receiver circuits typically include voltage-controlled-oscillator circuitry that is used for clock signal generation. In modern high speed wireless communications integrated circuits (e.g., integrated circuits that transmit and receive radio-frequency signals having frequencies that are higher than 1 GHz), LC-based voltage-controlled oscillators are used in circuits such as phase-locked loops. LC-based voltage-controlled oscillators (e.g., voltage-controlled oscillators that include inductors and capacitors) may exhibit desirable phase noise and jitter performance in comparison to ring-based voltage-controlled oscillators.
A conventional LC-based voltage-controlled oscillator (LC VCO) may suffer from high frequency noise injected at positive power supply and ground power supply terminals of the conventional LC VCO. Noise voltage injected at the positive and ground power supply terminals may undesirably affect the phase noise and jitter performance of the LC VCO.
The operating frequency range of a phase-locked loop may be limited by the frequency tuning range of its LC VCO. A conventional phase-locked loop typically includes a single LC VCO. The single LC VCO has a fixed inductor (i.e., an inductor that has a fixed inductance value) and a varactor (i.e., a voltage-controlled capacitor). Because the value of the inductance is fixed, the frequency tuning range of the oscillator is limited by the amount of capacitance tuning that can be achieved using the varactor.
It would therefore be desirable to be able to provide voltage-controlled-oscillator circuitry with improved phase noise performance and frequency tuning range.